Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with agraphical user interface according to an embodiment of the invention;and,

FIG. 2 is a front view of a second embodiment thereof.

The broken lines showing a display screen or portion thereof andelements of the graphical user interface illustrate portions of thearticle, and form no part of the claimed design.

CLAIM We claim the ornamental design for a display screen or portionthereof with a graphical user interface, as shown and described.